Reactor for Gasifying and/or Cleaning, Especially for Depolymerizing, Plastic Material and Associated Method

ABSTRACT

The invention relates to a reactor for gasifying and/or cleaning, especially for depolymerizing a plastic material ( 12 ), which reactor comprises: a reactor vessel ( 14 ) for receiving a starting material ( 12 ), especially the plastic material ( 12 ); a metal bath ( 26 ) which is arranged in the reactor vessel ( 14 ) and includes a liquid metallic material that has a metal bath melting temperature (T Schmelz ); a plurality of filling elements ( 25 ) in the metal bath ( 26 ); a heater ( 18 ) for heating the plastic material ( 12 ) in the reactor vessel ( 14 ); and a residual material removal device for at least partially removing residual material ( 38 ) which is produced during the gasification and/or cleaning of the starting material ( 12 ). According to the invention, the residual material removal device comprises an overflow which is centrally arranged in the reactor vessel ( 14 ) so that residual material ( 38 ) floating on the metal bath ( 26 ) can be removed via the overflow.

The invention relates to a reactor for gasifying and/or cleaning,especially for the depolymerizing of plastic material, with (a) areactor vessel for receiving a starting material, especially the plasticmaterial, (b) a metal bath which is arranged in the reactor vessel andincludes a liquid metallic material having a metal bath meltingtemperature, (c) a heating system for heating the plastic material inthe reactor vessel and (d) a residual material-removal device for atleast partially removing residual material which are produced during thegasification and/or cleaning of the starting material.

A reactor of this sort is described in WO 2010/130 404 and is used togasify plastic materials, in particular polymers. To this end, theplastic material is introduced into the reactor vessel of the reactor,for example by extruder, where it comes into contact with a metal bath.The high temperatures and, where applicable, the present catalyticeffect of the metal bath cause the depolymerization of the plasticmaterial.

The starting material may comprise materials, which are eithercompletely inert or not fully gasified, such that residual material isdeposited. This residual material must be removed from the reactorvessel so that it remains in constant operation. It has been proven thatthe removal of the residual material is a restrictive factor withregards to enabling an economic operation of the reactor.

The invention aims to improve the removal of residual material from thereactor vessel.

DE 197 35 153 A1 describes a method and a device for gasifying ofresidual material. For this purpose, the starting material to begasified is preferably introduced into a heated reactor, which haspreviously been filled with liquid slag, in such a way that an impulsecauses the slag to rotate. The organic elements of the starting materialare gasified and the mineral elements are fused and absorbed by theslag. This results in an increase in the volume of the slag. Should theslag volume exceed a particular limit, part of the slag runs through aside opening of a centrally located pipe in the reactor into a waterbath, where it then solidifies.

DE 196 29 544 C2 describes a method for processing polyvinylchloride. Inthis method, the PVC is also added to a rotating slag bath, in which agaseous part is separated off and the remaining material is absorbed bythe slag. The resulting slag is also directed through a central outflowinto a water bath.

The invention aims to improve the removal of the residual material fromthe reactor vessel.

The invention solves the problem by means of a reactor in accordancewith the preamble, wherein the residual material-removal devicecomprises an overflow which is centrally arranged in the reactor vesselso that residual material that floating on the metal bath can be removedvia the overflow. According to a second aspect, the invention solves theproblem by means of an operation method for a reactor of this sort thatincludes the following steps: (i) raising a gauge of a metal bath sothat the residual material enters the overflow, and (ii) removing theresidual material through the overflow.

It has been proven that a centrally situated overflow is particularlywell suited for the effective removal of residual material from thereactor vessel. It is thus advantageous if the overflow is always at thesame temperature as the metal bath surrounding it. This eliminates thepossibility of the residual material cooling down and clumping togetherupon removal.

A further advantage is that the gas development that occurs during theoperation of the reactor enhances the removal of the residual material.It is a surprising revelation that the gas development on the radialouter edge of the inner space of the reactor vessel is particularlylarge. The rising gas bubbles slightly raise the gauge of the metal bathover a period of time, such that the residual material floating on themetal bath experience a force acting radially inwards. This results in aradially inward flow of residual material, which can be removedparticularly effectively through the centrally located overflow.

The surprising realisation that the residual material has a preferreddirection of flow, namely radially inwards, also contributes to arelatively rapid movement of the residual material into the overflow. Ifthe overflow is arranged radially outwards, it may result in theformation of areas on the surface of the metal bath in which theresidual material residence time is so high that the residual materialclumps together. This results in the difficult removal of the residualmaterial from the reactor vessel.

The central location of the overflow does have the disadvantage that itis more difficult to exert an external influence, for example to removeresidual material that has stuck together. However, the above advantagesmore than compensate for this disadvantage.

The term reactor vessel should be understood in particular to mean adevice which, during operation, accommodates the metal bath, the fillingelement and the starting material.

The term metal bath should be understood to mean a concentration ofliquid metal, in particular molten metal, which takes the form of aliquid at an operating temperature of the reactor.

In particular, the metal bath comprises Wood's metal, the Lipowitzalloy, the Newton alloy, the Lichtenberg alloy and/or an alloy whichcontains gallium and indium. In principle, the metal bath has a densityof more than 9 grams per cubic centimetre, so that the starting materialexperiences a strong buoyant force. The metallic material has aparticular melting temperature of at least 300° C.

However, lower melting points are possible. The melting temperaturepreferably has a maximum value of 600° C. During operation of thereactor, the metal bath has a temperature of T from 300° C. to 600° C.

According to a preferred embodiment, the overflow consists of a removalpipe that is in thermal contact with the metal bath. This ensures thatthe removal pipe is of the same temperature as the metal bath, therebyavoiding the possibility of the materials clumping together when theycool down. The removal pipe is preferably a metal pipe, in particular aferromagnetic metal pipe.

The term heater should be understood in particular to mean a device bymeans of which the plastic material can be directly or indirectlyheated. In particular, the heater is an induction heater by means ofwhich one component of the reactor can be heated. For example, thefilling elements are ferromagnetic, so they can be heated by induction.However, it is conceivable that, in addition or alternatively to thefilling elements, the overflow and/or the reactor vessel areferromagnetic.

The starting material in particular is heated such that the fillingelements are heated, which in turn heat the metal bath. The metal baththen transfers the heat to the starting material.

The residual material removal device is in particular a device by meansof which the solid, fluid and/or paste-like matter that occurs duringgasification and/or cleaning can be removed.

According to a preferred embodiment, a residual material support deviceis arranged inside the removal pipe, which is designed to use amechanical impact to move residual material. For example, this may referto a screw conveyor that can scrape along the inside of the removal pipeso as to prevent or remove blockages.

The removal pipe preferably has an inner pipe diameter that is at leasta tenth of an inner reactor vessel diameter of the reactor vessel. Thisenables the efficient removal of the residual material.

It is beneficial if the residual material removal device comprises astorage vessel and a gas-tight lock, such that the storage vessel can bedetached from the reactor vessel, while remaining gas-proof in theprocess. In other words, it is possible to detach the storage vesselfrom the reactor vessel without allowing the gas to infiltrate thereactor vessel and escaping out of the storage vessel. This reduces therisk of fire, as otherwise flammable gases can escape.

In the following, the invention will be explained in more detail withthe aid of a drawing. It shows

FIG. 1 a reactor according to the invention for conducting a methodaccording to the invention.

FIG. 1 shows a reactor 10 for gasifying a starting material in the formof plastic material 12, in particular polyolefin polymers. The reactorcomprises, for example, an essentially cylindrical reactor vessel 14 forheating the plastic material 12, which is introduced into the reactorvessel 14 via an extruder 16.

The reactor 10 comprises a heater, for example an induction heater 18,which has a number of coils 20.1, 20.2, . . . , 20.4, by means of whichan alternating magnetic field is created in an inner space 22 of thereactor vessel 14. The coils 20 (reference numbers without a numericalsuffix refer to all respective object) are connected with a power supplyunit, not depicted, which induces an alternating current on the coils.The frequency f of the alternating current is, for example, in theregion of 4 to 50 kHz. Higher frequencies are possible, but they lead toan increase in the so-called skin effect, which is undesirable.

A deceleration device 24 is arranged in the inner space 22 of thereactor vessel 14, by means of which the upward flow of liquefiedplastic material 12 in the reactor vessel 14 can be slowed down. Thedeceleration device 24 comprises a number of movable filling elements25.1, 25.2, . . . arranged in the inner space 22. These elements aremade of ferromagnetic material and in the present invention take theform of spheres with a radius R. The sphere radius R may be between 0.5and 50 millimetres, for example.

As a result of their ferromagnetic properties, the filling elements 25are heated by the induction heater 18 and thereby heat a metal melt 26,i.e. molten metal, present in the reactor vessel 14. The specificationthat an object such as the filling elements 25 is made of ferromagneticmaterial means that the object is ferromagnetic at a room temperature of23° C.

The filling elements 25 have a Curie temperature T_(C,25,) above whichthe magnetic susceptibility χ sinks abruptly. The connection to theelectromagnetic field emitted by the induction heater suddenly becomessmaller and the filling element's 25 heat emission reduces dramatically.The heat input created by the induction heater is thus lower with hotfilling elements than cold filling elements.

The metal melt 26 has a melting point of T_(Schmelz)=300° C. and isintroduced into the reactor vessel 14 to a filling level of H_(füll).Along with the plastic material, it fills the spaces of the fillingelements 25. For example, the metal melt 26 is made of Wood's metal, theLipowitz alloy, the Newton alloy, the Lichtenberg alloy and/or an alloythat comprises gallium and indium. In principle, the metal melt 26 has adensity of at least 9 grams per cubic centimetre, so that the plasticmaterial 12 experiences a strong buoyant force. This buoyancyaccelerates the plastic material 12. The filling elements 25 counteractthis acceleration.

A temperature T prevails in the reactor vessel 14: this temperature isabove a reaction temperature T_(R) at which the plastic material 12gradually disintegrates. In this process, gas bubbles 28 are formed,which move upwards. The metal melt 26 can have a catalytic effect on thedisintegration process, such that the reactor 10 may refer to a thermocatalytic depolymerisation reactor. The plastic material 12 introducedvia the extruder 16 enters the inner space 22 through an entry opening30, which is preferably located on the base of the reactor vessel 14.

The deceleration device 24 may comprise restraint devices, such as agrid stretched across a frame, whose mesh is so small that the fillingelements 25 cannot move upwards through it. However, this is notnecessary. For example, a filling of spheres is sufficient, as depictedhere. The distribution of the filling elements 25, in the present casethe spheres, is schematically depicted in FIG. 1.

As a result of their buoyancy, one part of the filling elements 25floats in the metal melt 26 and another part is pressed into the metalmelt 26 by filling elements 25 that are positioned further up. Thefilling elements 25 are also depicted in FIG. 1 in a constant radius R.It is possible that the filling elements have variable radii, wherein,for example, the radius R decreases in an upward direction.

In addition to this, FIG. 1 depicts a removal pipe 36 arranged in thereactor vessel 14, via which the residual material 38 floating on themetal bath can be removed. In the present case, the removal pipe 36 runscoaxially to a longitudinal axis L of the reactor vessel 14. Theresidual material 38 is, for example, impurities of the plastic material12 and/or the additional catalyst which can be introduced via theextruder 16 or a second available extruder.

The removal pipe 36 can be made of ferromagnetic pipe material with apipe Curie temperature T_(C,36). As a result, the removal pipe 36 heatsup to T_(C,36) when the induction heater 18 is driven with asufficiently high power. The pipe material Curie temperature T_(C,36)may, for example, correspond to the filling element Curie temperatureT_(C,25, 1): it may also be lower or higher. However, it is alsopossible that the removal pipe 36 is constructed using anon-ferromagnetic material, such as an austenitic steel or titan.

The reactor vessel 14 is constructed of a wall material on at least theside facing the inner space 22. The wall material may be ferromagnetic,for example iron or magnetic steel. Alternatively, the wall material mayalso be non-magnetic.

If the wall material is ferromagnetic, it has a wall material Curietemperature T_(C,14). This may be lower than the filling element Curietemperature T_(C,25). In this case, the wall of the reactor vessel 14 iscolder during operation than the filling elements 25.

The removal pipe 36 is part of a pollutant removal system 40. As typicalresidual material impurities 38, such as sand, have a lower density thanthe metal bath 26, they float and can be removed at the top. Inaddition, the pollutant removal system 40 comprises a storage vessel,which may also be referred to as a settling tank 48, that collectsresidual material. The residual material 38 may contain not entirelydepolymerized organic material, alongside inorganic material. Theorganic material floats on the inorganic material and can be lead backinto the reactor vessel 14 through a recycling pipeline 50 on the bottomof the container.

The reactor 10 comprises a gas outlet 42 that flows into a condenser 44and removes the resulting gas. The fluid material leaving the condenser44 lands in a collector 46.

The reactor described can be operated with, for example, waste oil as astarting material instead of plastic material, and then be used forrecycling and processing.

A method according to the invention is conducted by initially raisingthe gauge H_(füll), for example, by introducing the metal bath 26 to thereactor vessel 14. This may occur by introducing solid metal spheresmade of the metallic material into the reactor vessel 14 so that theymelt. It is also possible to increase the flow of plastic material 12,in particular by operating the extruder at a higher power. Thisincreases the volume of both gasified and non-gasified plastic materialpresent in the reactor vessel 14, so that the gauge H_(füll) rises, forexample in the form of the removal pipe 36. The residual material 38 arethen removed: this means that they either automatically flow through theremoval pipe or they are transported through the removal device by acorresponding device, in the present case the removal pipe 36.

It can be advantageous to lower the supply of plastic material prior toraising the metal gauge so as to reduce the formation of gas bubbles.This has the advantage that less gas bubbles form, thereby decreasinglosses in the metal bath caused by splattering.

The gauge will preferably be lowered again after raising the gauge inthe metal bath and removing the residual material through the overflow,for example by draining the metal bath.

It is preferable if a gauge of the metal bath is set such that theresidual material layer is set at a thickness H₃₈ of at least 10 cm,whereby the thickness H₃₈ may fall below this value when the metal bathgauge is raised for the removal of the residual material through theoverflow.

In other words, the fact that the residual material layer has athickness H₃₈ of at least 10 cm should be understood to mean that thisthickness is achieved and exceeded at least 75% of the time. Thethickness H₃₈ is the distance from the boundary layer between the metalbath and residual material layer to the upper edge of the residualmaterial layer on the other. The thickness is preferably regulated bymeans of a feedback control system. This means that the reactor 10 has athickness registration device, which is not depicted, by means of whichthe thickness Has can be recorded. Should a maximum thickness Has beexceeded, the above described method for the removal of residualmaterial is conducted.

REFERENCE LIST

10 Reactor 12 Plastic material 14 Reactor vessel 16 Extruder 18Induction heater 20 Coil 22 Inner space 24 Deceleration device 25Filling elements 26 Metal bath 28 Gas bubble 30 Entry opening 32Catalyst 34 Outer wall 36 Removal pipe 38 Residual material 40 Pollutantremoval system 42 Gas outlet 44 Condenser 46 Collector 48 Settling tank50 Recycling pipeline χ Magnetic susceptibility f Frequency LLongitudinal axis R Sphere radius H_(full) Filling height, gauge H₃₈Thickness d₁₄ Reactor vessel inner diameter d₃₆ Pipe inner diameterT_(Schmelz) Metal bath melting temperature T Temperature T_(R) Reactiontemperature T_(C,36) Pipe material Curie temperature T_(C,25) Fillingelement Curie temperature T_(C,14) Wall material Curie temperature

1. A reactor for gasifying and/or cleaning, especially for depolymerizing plastic material, with (a) a reactor vessel for receiving a starting material, especially a plastic material, (b) a metal bath, which is arranged in the reactor vessel and includes a liquid metallic substance that has a metal bath melting temperature (TSchmelz), (c) a plurality of filling elements in the metal bath, (d) a heater for heating the plastic material in the reactor vessel and (e) a residual material-removal device for at least partially removing residual material which is produced during the gasification and/or cleaning of the starting material, characterised by the fact that (f) the residual material removal device comprises an overflow centrally arranged in the reactor so that residual material floating on the metal bath can be removed via the overflow.
 2. The reactor according to claim 1, characterized by the fact that the overflow consists of a removal pipe that is in thermal contact with the metal bath.
 3. The reactor according to claim 2, characterized by the fact that a residual material support device is arranged inside the removal pipe, which is designed to use a mechanical impact to move residual material.
 4. The reactor according to claim 2, characterized by the fact that the removal pipe has an inner pipe diameter that is at least a tenth of an inner reactor vessel diameter of the reactor vessel.
 5. The reactor according to claim 1, characterized by the fact that the residual material removal device comprises a storage vessel and a gas-tight lock, such that the storage vessel can be detached from the reactor vessel, while remaining gas-proof in the process.
 6. A method for the operation of a reactor for gasifying and/or cleaning, especially for the depolymerizing plastic material, which has (a) a reactor vessel for receiving plastic material, (b) a metal bath, which is arranged in the reactor vessel and includes a liquid metallic substance that has a metal bath melting temperature (TSchmelz), (c) a heater for heating the plastic material in the reactor vessel and (d) a residual material removal device for at least partially removing residual material which is produced during the gasification and/or cleaning of the plastic material, which comprises an overflow centrally arranged in the reactor so that the residual material floating on the metal bath can be removed via the overflow, with the steps: (i) raising a gauge of a metal bath so that the residual material enter the overflow, and (ii) removing the residual material through the overflow.
 7. The method according to claim 6, characterized by the steps: the introduction of plastic material into the reactor vessel, wherein the introduction of plastic material into the reactor vessel and/or the setting of the gauge in the metal bath is conducted such that a residual material layer made of residual material forms on the metal bath, wherein the residual material layer has a thickness of at least 10 centimetres. 